System for processing large xerographic prints

ABSTRACT

PRESENT XEROGRAPHY SYSTEMS IMPRESS AN IMAGE ON AN ELECTROSTATIC SHEET OR FILM BY CHARGING THE ENTIRE AREA OF THE SHEET AND THEN EXPOSING THAT AREA TO THE IMAGE AND THEN APPLYING TONER TO THAT AREA TO DEVELOP THE IMAGE IMPRESSED ON THE FILM TO PERMANENT VISIBLE FORM. THE PRESENT SYSTEM CHARGES, EXPOSES AND TONES A LARGE AREA ELECTROSTATIC SHEET OR FILM IN SECTIONS BY POSITIONING A VERTICALLY MOVING CURTAIN BETWEEN THE FILM AND THE LENS SYSTEM. HORIZONTAL CORONA DISCHAGE PRODUCING ELECTRODES, A HORIZONTAL WINDOW AND THE HORIZONTAL WIPER BLADE ARE SPACED ONE ABOVE THE OTHER ON THE CURTAIN. AS THE CURTAIN MOVES DOWNWARD, AND ELECTRODES CHARGE PROGRESSIVELY LOWER AREAS OF THE FILM ACROSS ITS FULL WIDTH. THEN THE DOWNWARDLY MOVING HORIZONTAL WINDOW EXPOSES THESE AREAS, IN TURN, TO PROGRESSIVELY LOWER PORTIONS OF THE IMAGE PROJECTED FROM THE LENS SYSTEM SO THAT A LATENT IMAGE IS FOUND ON THE FILM. FINALLLY, THE DOWNWARDLY MOVING WIPER BLADE SPREADS TONER FROM AN ADJACENT SUPPLY UNIFORMILY OVER PROGRESSIVELY LOWER AREAS OF THE EXPOSED FILM SO THAT A HIGH-QUALITY VISIBLE IMAGE IS IMPRESSED ON THE FILM.

June 20, 1972 M. R. KUEHNLE 3,571,120

SYSTEM FOR PROCESSING LARGE XEROGRAPHIC PRINTS Filed Sept. 28, 1970 2 sheets-sheet 1 INVENTOR MANFRED. R KUEHNLE l 1 l i \l/ BY ATTORNEYS June 20, 1972 M. R. KUEHNLE 3,671,120

Filed Se t 28, 1970 2 Sheets-Sheet Z FIG. 2A

FIG. 2B

INVENTOR MANFRED R. KUEHNLE ATTORNEYS United States Patent Ofice 3,671,120 Patented June 20, 1972 US. Cl. 355-8 13 Claims ABSTRACT OF THE DISCLOSURE Present xerography systems impress an image on an electrostatic sheet or film by charging the entire area of the sheet and then exposing that area to the image and then applying toner to that area to develo the image impressed on the film to permanent visible form. The present system charges, exposes and tones a large area electrostatic sheet or film in sections by positioning a vertically moving curtain between the film and the lens system. Horizontal corona discharge producing electrodes, a horizontal window and a horizontal wiper blade are spaced one above the other on the curtain. As thecurtain moves downward, the electrodes charge progressively lower areas of the film across its full width. Then the downwardly moving horizontal window exposes these areas, in turn, to progressively lower portions of the image projected from the lens system so that a latent image is found on the film. Finally, the downwardly moving wiper blade spreads toner from an adjacent supply uniformily over progressively lower areas of the exposed film so that a high-quality visible image is impressed on the film.

BACKGROUND OF THE INVENTION This invention relates to a system for making film transparencies and prints by xerography. It relates more particularly to a system for making relatively large area xerographic prints and transparencies which are characterized by their relatively high quality.

Conventional xerography systems impress visible images on a sheet or film by charging the entire film and then exposing it to develop a latent image on the film. Finally, toner is applied to the film to reduce the latent image to permanent visible form. This technique has worked quite satisfactorily with relatively small area prints and transparencies, i.e. on the order of 15 by 15 inches. However, when one attempts to make large area xerographic prints and transparencies, e.g. on the order of 30 by 30 inches and larger, using the usual xerography techniques, the results are not always satisfactory. The reasons for this are two-fold. First, conventional charging techniques may not impress a uniform electrostatic charge over a large area. Consequently, the latent image impressed on the charged sheet may not correspond accurately to the image projected from the lens system. Secondly, using conventional procedures, it is very difficult to apply the toner uniformly over the entire area of the sheet or film. Therefore the visible image produced on the film may not correspond accurately to the latent image thereon. As a result of these variables, the lines making up the photographic image tend to be of varying intensity and are sometimes indistinct, with the result that the overall photographic image is of relatively poor quality.

SUMMARY OF THE INVENTION The present invention aims to provide a xerography system which is capable of making large-area, high quality xerographic prints and transparencies.

A further object of the invention is to provide such a system which is relatively easy to make and maintain.

Another object of the invention is to provide a system which makes enlarged xerographic prints or transparencies directly.

Yet another object of the invention is to provide a system of this type which is easy to operate.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the invention will be indicated in the claims.

Briefly, the present xerography system processes a largearea xerographic sheet or film in a progressive fashion. The film is positioned on the lens axis of an image-projecting lens system. An opaque curtain is situated between the film and the lens so that it normally prevents projected light from striking the film.

The curtain carries a pair of long, closely-spaced corona discharge producing electrodes which extend across the width of the curtain (and the film). When these electrodes are energized, they develop a narrow horizontal band of corona discharge. The curtain also has a relatively narrow horizontal window spaced above the electrodes. The area of this window corresponds to the area of the corona discharge produced by the electrodes. Finally, a relatively narrow, horizontal wiper blade is attached to the curtain above the window.

When the curtain is moved downwards, first the electrodes, then the window, and finally the wiper blade, are drawn down along the face of the film. As the electrodes move along the film, progressively lower areas of the film are charged. Then, as the window moves along the film behind the electrodes, progressively lower parts of the projected image from the lens system are incident on progressively lower charged areas of the film. Finally, as the wiper blade moves downward along the film behind the window, it spreads toner from a supply adjacent the top of the film smoothly and evenly over progressively lower exposed areas of the film.

Thus when the wiper blade reaches the bottom of the film, the entire image projected from the lens system is permanently impressed on the film. The curtain then returns to its initial position and the film is removed, completing the cycle.

If desired, the curtain may also include a heating element spaced above the wiper blade which can develop sufficient heat to more rapidly dry the toner on the film, and thereby speed up the printing process.

It is apparent then that the present system performs the different steps in the xerography process separately but continuously on relatively small areas of a much larger film. These areas are small enough to be charged and toned uniformly so that the portions of the total photographic image impressed on these areas have the quality and clarity of small xerographic prints or transparencies made in the usual way. Consequently, the entire film, which is the sum of these parts, has comparable quality and clarity.

Furthermore, while the present system employs a single step process to make xerographic enlargements, it is still relatively simple and inexpensive to make and can be operated and maintained by relatively unskilled personnel.

BRIEF DESCRIPTION OF THE DRAWINGS 'For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view with portions developed in dotted lines of a system for making xerographic enlargements embodying the principles of my invention;

FIG. 2A is a side elevation of the portion of the FIG. 1 system at one point in its operating cycle; and

FIG. 2B is a similar view at another point in the operating cycle of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENT The entire xerography system is enclosed in a housing 10. It includes a projection section shown generally at 12 which projects a still image to be impressed on a large-area electrostatic sheet or film 22. The system also includes a processing section shown generallyat 14 which processes the image projected onto the film 22 into permanent visible form.

For purposes of discussion, we will talk in terms of an enlarged film or transparency. However, it should be understood that the present system is also equally capable of making print enlargements.

Projection section 12 generates an image in the usual way from a transparency or print. This image is then projected through a lens system 16, having an optical axis A, toward the processing section 14.

A suitable frame assembly 24 mounted within housing supports film 22 so that it is centered on lens axis A. Frame assembly 24 is designed to permit ready removal of the film and replacement by another similar film. Of course the lens system 16 is arranged so that an image of a size comparable to the size of film 22 is brought to focus at the opposing face of the film.

An opaque, flexible curtain or sheet 26 is positioned adjacent the face of film 22 opposite lens system 16.

Curtain 26 is stretched between a let-off spool 28 and a take-up spool 32. Also a transparent glass or plastic platen 34 is supported within the housing and biased by any suitable means such as springs 35 towards frame assembly 24 so that it presses curtain 26 fiat against the film 22 in the frame assembly.

Curtain 26 can be wound in either direction between the two spools 28 and 32 so that it slides up and down in the space between film 22 and platen 34. Preferably the upper and lower edges 34a of the platen are beveled on the side adjacent the curtain to facilitate this movement.

Curtain 26 is moved by any convenient means. In the present illustration, the let-off spool 28 is springloaded so that it tends to wind up curtain 26. On the other hand, the take-up spool 32 is connected by way of normally engaged solenoid clutch 36 to a geared down electric motor 38. When motor 38 is energized and clutch 36 is deenergized, spool 32 is rotated so that the curtain 26 is slowly pulled downwards and rolled up on spool 32. After the curtain has reached the end of its travel, clutch 36 is energized, thereby disengaging the spool 32 from the motor so that the curtain 26 is immediately rolled up again on the spring-loaded spool 28. As soon as the solenoid 36 is deenergized again, the curtain will again move slowly downwards as it is wound up on spool 32, and so on.

Still referring to FIG. 1, film 22 is processed by various elements carried by curtain 26. For purposes of clarity, we have shown in dotted lines a development of the portion of the curtain wound up on spool 28 in order to show more clearly these elements on the curtain. The terms above and below as used herein refer to relative positions on the developed portion of the curtain 26.

More particularly, a pair of narrow corona discharge producing wire electrodes 42a and 42b are affixed to the curtain on the side thereof facing film 22. These electrodes extend substantially the full width of the curtain (and the film 22) and they are closely spaced one above the other. These electrodes are connected by means of long, flexible connectors 44a and 44b to a power supply 46. When supply 46 is turned on, a corona discharge 4 is developed in a generally rectangular area around the electrodes 42a and 42b.

Also a window or slit 48 is formed in curtain 26 directly above the electrodes 42a and 42b. The shape and area of window 48 is substantially the same as the shape and area of the corona discharge produced by the energized electrodes.

In addition curtain 26 carries a horizontal wiper blade 52 spaced above window 48. Blade 52 projects out from the side of the curtain facing film 22 and extends substantially the entire width of the curtain and film.

Normally, curtain 26 is wound up on spool 28. In this condition electrodes 42a and 42b are positioned just above the frame assembly 24 and the slit 48 and wiper blade 52 are on the curtain portion wound up on spool 28. To operate the system a film 22 is placed in assembly 24. Then the power supply 46 is turned on either manually or automatically and the projection section 12 is caused to project an image toward the film in assembly 24. It should be emphasized, however, that the opaque curtain 26 prevents any of the projected light from stricking the film.

Now, with the motor 38 running, clutch 36 is engaged so that spool 32 commences winding up the curtain 26. As the curtain moves downwards, the electrodes 42a and 42b are drawn downwards across the face of film 22. The corona discharge developed by these electrodes impresses an electrostatic charge on progressively lower horizontal bands or areas of film 22.

Turning now to FIG. 2A, as the curtain 26 continues moving downwards, window 48 is drawn down along the face of film 22. This allows progressively lower bands or areas of the film to be exposed to progressively lower portions of the projected image from lens system 16. Those charged portions of the film 22 which are struck by light from lens system 16 (corresponding to light areas in the original image being projected) are discharged. On the other hand, those portions which do not receive this incident light (corresponding to the darkened ,areas on the image being projected) remain charged.

Thus, by the time the window 48 has reached the bottom of the film, the entire area of film 22 has been charged and exposed to the image from lens system 16 so that a corresponding latent image is impressed on film 22.

In the meantime, however, as the curtain 26 continues moving downwards, wiper blade 52 is drawn along the face of film 22 as shown in FIG. 2B. Just after the blade arrives at the top of film 22, liquid toner 53 from a toner dispenser 54 is dispensed onto the top of blade 52 between film 22 and curtain 26. More particularly, as best seen in FIGS. 1 and 2A, dispenser 54 has a wide mouth 54a which extends to curtain 26 between the let-off spool 28 and the top of the frame assembly 24. When a solenoid actuated valve 56 on the side of the dispenser is energized, a measured amount of liquid toner is deposited onto blade 52.

Preferably, the top surface 52a of blade 52 is slightly concave to hold the toner so dispensed. Thus, as blade 52 proceeds downwards along the face of film 22, the toner is spread evenly and uniformly over progressively lower areas of the film along their entire widths.

The toner adheres to those portions of the film 22 which still carry an electrostatic charge, i.e. those portions corresponding to the dark areas of the projected image from lens system 16. On the other hand, toner does not adhere to the uncharged areas of the film, i.e. those corresponding to the light areas of the projected image.

Thus after the blade 52 has reached the bottom of film 22, toner has been applied to the entire latent image on the film so that that image is reduced to permanent visible form. At this point, clutch 36 is energized, thereby disengaging spool 32 from motor 38, with the result that the curtain 26 is immediately wound upon the spring loaded let-olf roll 28, completing the cycle.

The finished film 22 can now be removed from frame assembly 24 and replaced by another similar film which is to receive the next projected image from section 12.

Operation of the power supply 46, clutch 36, motor 38 and solenoid valve 56 can be controlled manually by the operator or in a timed sequence using a conventional timing device.

In order to speed up the printing process, it may be desirable to heat the toner applied to film 22. One way of accomplishing this is to hinge the assembly 24 so that it can be swung back as shown in dotted lines in FIG. 1 and then to direct heated air from a blower 62 onto the surface of the film therein. Another way of doing this is to include a flexible heating element 64 as shown in dotted lines in FIG. 1 in the curtain above wiper 52. When an electric current is supplied to the heating element as it proceeds downward along the film 22, sufiicient heat is developed to rapidly evaporate the toner solvent thereby quickly fusing the toner to the film. Also it may be desirable to maintain a humid atmosphere in the vicinity of the film so that the film retains its charge even in a dry climate. This may be accomplished by any convenient means.

-It will be seen from the foregoing then that the present system is able to print directly large area xerographic prints and films in one continuous operation. Still, however, the quality and clarity of the printed images are quite high because only relatively small areas of the film are processed at any one time. Finally, the present system is relatively simple to make and to operate and should be comparable in cost to conventional xerography apparatus.

It will thus be seen that the objects set forth above, among those apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described.

I claim:

1. A system for making large xerographic prints and transparencies comprising (A) a lens system for projecting an image,

(B) means for holding a film of material capable of retaining an electrostatic charge in a stationary position to receive the image projected by the lens system,

(C) means opaque to the light from the lens system positioned adjacent the holding means so as to normally prevent the projected light from striking film in the holding means,

(D) processing means carired by the opaque means,

said processing means including (1) means for impressing an electrostatic charge on the film in the holding means,

(2) a window in the opaque means spaced from the charge applying means, and

(3) means spaced from the window on the other side thereof from the charge applying means for applying toner to film in the film holding means, and

(E) means for moving the opaque means so that first the charge applying means, then the window, and finally the toner applying means are drawn along the face of fihn in the film holding means so that adjacent portions of the film are progressively charged, then exposed to adjacent portions of the image projected from the lens system through the window and then spread with toner whereby a permanent photographic image is impressed progressively on the sheet.

2. The system as defined in claim '1 and further including a source of toner positioned adjacent the film holding means for dispensing toner onto the applying means prior to their travel across the film in the film holding means.

3. The system as defined in claim 1 (A) wherein the opaque means is a flexible curtain,

and

(B) further including (1) take-up and let-off spools supporting opposite ends of the curtain, and

(2) means for rotating at least one of the spools so as to draw the curtain along the face of the film in the film holding means.

4. The system defined in claim 3 and further including means for rotating at least one of the spools in the opposite direction so that the curtain returns to its initial position after processing the film.

5. The system defined in claim 1 and further including (A) a transparent platen adjacent the opaque means on the side thereof facing the lens system, and

(B) means for urging the platen toward the opaque means so as to press the elements thereon against the film in the film holding means.

6. A system for making xerographic enlargements comprising (A) means for holding a sheet or film capable of retaining an electrostatic charge in a stationary position, and

(B) a curtain positioned adjacent the film holding means so as to normally prevent light from striking film in the film holding means, said curtain (1) being movable in a selected direction substantially parallel to the film holding means,

(2) means carried by the curtain for applying an electrostatic charge progressively to adjacent portions of the film in the film holding means as the curtain moves in the selected direction,

(3) a window in the curtain adjacent the charge applying means which progressively exposes the charged portions of film in the film holding means to adjacent portions of an image projected toward the film as the curtain moves in the selected direction, and

(4) means on the curtain spaced from the window [for progressively applying toner to the exposed portions of the film in the film holding means as the curtain moves in the selected direction so as to produce a permanent visible image on the film.

7. The system defined in claim 6 and further including a transparent platen adjacent the curtain, said platen being biased toward the film holding means so as to press the intervening curtain against the film in the film holding means.

8. The system as defined in claim 6 and further including means for dispensing liquid toner onto the toner applying means prior to their travel across the film in the film holding means.

9. The system as defined in claim 6 (A) wherein the curtain is stretched between a pair of spools, and

(B) further including (1) means for driving at least one of the spools so that the curtain moves in the selected direction at a selected speed, and

(2) means for rotating at least one of the spools in the opposite direction to move the curtain in the opposite direction so that it returns to its initial position.

10. The system defined in claim 6 wherein the charge applying means comprise (A) a pair of electrodes mounted on the curtain, and

'(B) means for applying a voltage across the electrodes.

8 11. The system as defined in claim 6 and further includ- References Cit d ing a projection system for projecting an image toward UNITED STATES PATENTS the film in the film holding means.

'12. The system as defined in claim 6 and further includ- 2,816,493 12/ 1957 Lewis et a1 X ing means for applying heat to the toner after it is applied to the film in the film holding means.

13. The system defined in claim 8 wherein the toner dispensing means comprise (A) a container for li uid toner, (B) means for conducting toner from the container to 10 SAMUEL MATTHEWS Primary Examiner a region adjacent the curtain on the side thereof R. P. GREINER, Assistant Examiner facing the film, and (C) means for metering toner from the container onto the toner applying means when they approach said 35510,

region. 15

FOREIGN PATENTS 1,931,683 1/1970 Germany v- 355-8 6714238 4/1968 Netherlands 355-8 

